兰州-西宁-银川城市带与西部开发   总被引：15，自引：2，他引：13  

汪一鸣  杨汝万  吴永辉 《地理学报》2004,59(2):213-222

通过对有关城市、区域的统计分析,在评述兰州-西宁-银川城市带基本特征的基础上,重点讨论其在西部大开发中四个方面的地位作用：我国内陆腹地的战略要地和开发据点,沟通我国东西部间、我国与中亚、欧洲国家间的桥梁和纽带,保障国家资源安全的能源重化工基地和重要进口通道,保障国家生态安全的重点生态建设区。并针对其在内部结构、市场化、开放度方面的主要问题,指出其发展趋势和战略选择：加快城市带交通通道建设,将潜在资源优势转化为现实经济优势,创造局部优势投资环境和开放社会,重视教育、科技和生态建设。  相似文献   

Remote sensing mapping of the regeneration of coastal natural habitats in Singapore: Implications for marine conservation in tropical cities     

Y. H. Jonathan Tan  Jacqueline K. Q. Tham  Aayush Paul  Umair Rana  Hui Ping Ang  Nhung T. H. Nguyen  Alex T. K. Yee  Bryan P. I. Leong  Simon Drummond  Karenne P. P. Tun 《Singapore journal of tropical geography》2023,44(1):130-148

Rapid urbanization has resulted in the loss of coastal and marine habitats in cities worldwide. The effective conservation of urban coastal ecosystems requires detailed knowledge of their spatial distribution, necessitating high-resolution mapping. Our study produces a high-resolution coastal and marine habitat map and shoreline map for the tropical city-state of Singapore created through pixel-based supervised classification of satellite imagery, bathymetry data and expert ground knowledge. These maps can be used as a base reference for multiple applications including ecological research, conservation and urban planning. They also help identifiy trends in the extent of key coastal habitats, providing insight into their differing levels of vulnerability to loss and potential for restoration to ensure long-term resilience. The method used for mapping shoreline typologies and resulting insights gained, can guide other rapidly urbanizing coastal cities on strategies to assemble useful spatial knowledge for effective conservation of their urban coastal ecosystems.  相似文献   

Parametric analyses of push-out tests and implications for design of rock-socketed steel H-pile     

Y.D. Zhou  L.G. Tham  X.W. Tang  Y.T. Liu  M.K. Wong 《Computers and Geotechnics》2011

The load response of a rock-socketed steel H-pile can be strongly influenced by the nonlinear interfacial behavior between the grout and the steel H-pile, and between the pile and the rock mass. This paper focuses on the load-transfer mechanism of the former interface through experimental push-out tests and numerical simulation of the tests. The study is divided into two parts. In the first part, a series of push-out tests have been carried out on four types of specimens (with studs + confinement (Case I); no stud + confinement (Case II); no stud + no confinement (Case III); and studs + no confinement (Case IV)). The second part is a numerical study based on three-dimensional finite element technique, which takes into account possible damage and cracking in grout, as well as bond-slip along the interface. It is shown that the numerical predictions of the four cases compare favorably with the corresponding test results, including the load–displacement response and the development of cracks. Furthermore, parametric study has been carried out to investigate the influence of various factors, including the studs, the casing confinement, the grout fracture energy, and the dilation property of steel-grout interface. Lastly, some implications, based on the test and numerical results, on the design of socketed steel H-piles are discussed.  相似文献   

A 3-D time-domain coupled model for nonlinear waves acting on a box-shaped ship fixed in a harbor     

王大国  邹志利 《中国海洋工程》2011,25(3):441-456

A 3-D time-domain numerical coupled model is developed to obtain an efficient method for nonlinear waves acting on a box-shaped ship fixed in a harbor. The domain is divided into the inner domain and the outer domain. The inner domain is the area beneath the ship and the flow is described by the simplified Euler equations. The remaining area is the outer domain and the flow is defined by the higher-order Boussinesq equations in order to consider the nonlinearity of the wave motions. Along the interface boundaries between the inner domain and the outer domain, the volume flux is assumed to be continuous and the wave pressures are equal. Relevant physical experiment is conducted to validate the present model and it is shown that the numerical results agree with the experimental data. Compared the coupled model with the flow in the inner domain governed by the Laplace equation, the present coupled model is more efficient and its solution procedure is simpler, which is particularly useful for the study on the effect of the nonlinear waves acting on a fixed box-shaped ship in a large harbor.  相似文献   

石灰土发育过程中土壤腐殖质组成及其与土壤钙赋存形态关系   总被引：6，自引：2，他引：4  

陈家瑞  曹建华  梁毅  杨慧 《中国岩溶》2012,31(1):7-11

选取桂林典型石灰土不同发育阶段土样(黑色石灰土、棕色石灰土、黄色石灰土),对土壤中腐殖质组成、土壤钙的形态及其含量进行测定。结果显示:(1)石灰土发育过程中,黑色石灰土、棕色石灰土、黄色石灰土总碳量分别为230.15mg/g、37.49mg/g、17.94mg/g,胡敏酸所占比例分别为31.94%、9.44%、7.25%,富啡酸所占比例为1.04%、36.14%、66.16%,胡敏素为67.02%、54.41%、26.59%;(2)黑色石灰土、棕色石灰土、黄色石灰土中土壤钙全量分别为21486.66mg/kg、6913.33mg/kg、5540.17mg/kg,且三种土壤中均是酸溶态所占比例最高,分别为57.58%、74.69%、80.83%,其次为可还原态、残渣态和可氧化态;(3)相关性分析表明,土壤钙及其各形态均与土壤有机碳总量、胡敏酸、胡敏素成正相关关系,与富啡酸成负相关关系,土壤腐殖质组成及其含量在很大程度上影响着土壤钙含量及赋存形态。   相似文献   

正断层诱发砂土中群桩基础破坏及避让距离研究     

蔡奇鹏  甘港璐  吴宏伟  陈星欣  肖朝昀 《岩土力学》2019,40(3):1067-1075

地震中发震断层诱发桩基失效,导致上部结构破坏甚至坍塌,相关破坏机制和避让距离缺乏系统研究。通过离心机试验和数值模拟,针对基岩正断层活动诱发上覆砂土中群桩基础的静力破坏展开研究,考察不同群桩断层相对位置下群桩的破坏特征。试验与计算结果均表明,当群桩跨越断层时,正断层活动使群桩向上盘一侧倾斜,并使基桩弯向上盘一侧。基桩桩顶荷载的重分布进一步使基桩形成受拉和受压两种破坏模式。数值参数分析表明,在不同桩位上,群桩的变形响应可划分为5个特征区域。对于埋深为20.0 m的基岩正断层,群桩在上盘和下盘一侧的安全避让距离分别为23.5 m和15.9 m,其中下盘一侧离开断层7.9 m至上盘一侧离开断层4.1 m的区域需要进行重点避让。  相似文献   

Deformation and crack development of a nailed loose fill slope subjected to water infiltration   总被引：1，自引：0，他引：1  

Y. D. Zhou  C. Y. Cheuk  L. G. Tham 《Landslides》2009,6(4):299-308

The paper presents the characteristics of progressive movement and crack development observed in a loose fill slope reinforced by soil nails subjected to water infiltration. The purpose-built test slope was constructed by end-tipping completely decomposed granite on moderately gentle sloping ground with minimal compaction, and two rows of soil nails were installed after completion of the slope. Based on the field monitoring data obtained from a comprehensive instrumentation system, this field test has identified the initiation and development mechanism of deformation, including crack propagation in the test slope. The test results on the temporal and spatial variation of wetting-induced movement, water content distribution, and suction change as well as the formation and propagation of surficial cracks are presented. The causative mechanisms of wetting-induced deformations and their implications on the stability of nailed fill slopes are also presented and discussed.  相似文献   

A New Magnetically Active Binary System Discovered in Yunnan-Hong Kong Wide Field Survey     

WANG Jian-hua  GU Sheng-hong  WANG Xiao-bin  Bill YEUNG  Eric NG 《Chinese Astronomy and Astrophysics》2021,45(1):67-81

We present a newly discovered magnetically active binary system detected by Yunnan-Hong Kong wide field survey, with an orbital period of 0.60286 days. Two color photometry for the system was performed using the 1 m Cassegrain telescope of Yunnan Observatories with its CCD (Charge-Coupled Device) camera. In the observed light curves, there are clearly different light maxima existed in the out-of-eclipse regions. We made spectroscopic observations for the binary system using the 2.4 m telescope and YFOSC (Yunnan Faint Object Spectrograph and Camera) of Lijiang station of Yunnan Observatories, China. The radial velocity curve was derived for primary star of the binary system. The primary star exhibited strong chromospheric activity, which confirms that the distortion of the light curves results from the starspot activity on the primary star. Through analyzing the light curves and RV (Radial Velocity) curve mentioned above by means of the W-D (Wilson-Devinney) code, orbital parameters and starspot configuration of the binary system are obtained. Finally, we have discussed the properties of the binary system, and given the prospects on the future work.  相似文献   

On the Relationship Between Killing-Yano Tensors and Electromagnetic Fields on Curved Spaces     

NG. Ibohal 《Astrophysics and Space Science》1997,249(1):73-93

The existence of skew symmetric Killing-Yano (KY) tensors of order 2 has been investigated on curved spaces. The integrability conditions of KY tensor including Carter's algebraic relation of symmetric tensor with electromagnetic field have been transcribed in Newman-Penrose formalism. The KY bivectors are classified according to their nullity in electrovac space-times. It is shown that the non-null (or null) electromagnetic field implies to the existence of non-null (or null) KY tensor. Thus Collinson's theorems on the existence of KY tensors on vacuum space-times have been generalized on electrovac space-times. Chandrasekhar's theorem on vacuum type D space-times has also been generalized on the existence of non-null KY tensor on electrovac type D or non-vacuum type D space-time filled with dust. All theorems presented here have been strengthened by giving examples for known space-times. It is also shown that most of KY tensors discussed here are eigen-KY-bivectors of the respective curvature tensors.  相似文献   

Magnetic susceptibility as a possible correlation tool in Quaternary alluvial stratigraphy          下载免费PDF全文

Zoltán Püspöki  István J. Kovács  Tamás Fancsik  Annamária Nádor  Edit Thamó‐Bozsó  Ágnes Tóth‐Makk  Beatrix Udvardi  Péter Kónya  Judit Füri  Zsolt Bendő  László Zilahi‐Sebess  Ferenc Stercel  Ágnes Gulyás  Richard W. Mcintosh 《Boreas: An International Journal of Quaternary Research》2016,45(4):861-875

Correlation of the fluvial magnetic susceptibility (MS) record of borehole Devavanya‐1 in the Körös Basin (eastern Hungary) with Chinese aeolian MS records (Jingbian, Lingtai) and the marine δ¹⁸O record from the Equatorial Pacific (V28‐239) is established here based on cross‐correlations and singular spectral analysis. A basin‐scale well‐to‐well correlation based on magnetic susceptibility records was also performed involving unpublished cores. To refine the age model, a Monte Carlo simulation was conducted using the Chinese Jingbian section as a tuning target. Spectral analysis of the tuned record revealed c. 400, c. 100 and c. 41 ka cycles over the 2.5 million years of the Quaternary fluvial succession. To ensure a complementary palaeoclimate proxy, the full width at half maximum of smectites was measured as a facies‐independent indicator of weathering intensity. This investigation was carried out on a subset of samples involved in MS measurements representing a c. 400 ka time interval across the top of the Olduvai subchron. A phase‐shift between MS and weathering intensity recorded in the clay mineralogy indicates different response times of the considered proxies. The fluvial MS record is determined by the climatic control on delivery and preservation of magnetic minerals, mainly of magnetite. Under cold‐and‐dry climate these minerals were released owing to frost shattering in the adjacent hinterlands and were transported to alluvial plains in the early postglacial periods thanks to the increasing discharge of rivers. With further warming the weathering‐sensitive magnetic minerals soon disappeared from the soils of the catchment area and thus from the fluvial load. As a result, in fluvial successions early postglacial warmings are expressed by the occurrences of MS maxima (magnetic episodes), while the palaeotemperature maximum and the subsequent cooling remain concealed within the tract of low MS values. The early postglacial magnetic episodes may serve as ideal stratigraphical markers in regional and global correlations.  相似文献